The veterinary studies area conducts investigations using veterinary morbidity and mortality data from university teaching hospitals in North America, the Armed Forces Institute of Pathology, NCI's Registry of Experimental Cancers, and other sources. These studies investigate the role of genetic and environmental factors on the etiology of cancer in animals and generate hypotheses for testing in companion humans and other human populations. Major areas of interest include the effects of household exposure to pesticides among pet dogs and their companion humans, and studies of cancer and other conditions among U.S. military working dogs (MWD) who served in Vietnam relative to that among other MWDs who served elsewhere, with linkeage to health conditions that occurred among their human handlers (N=20,000). Other studies of the effects of the Vietnam experience are being conducted using a cohort of West Virginia residents who served in Vietnam (N=41,000) relative to the health experience among those who served elsewhere (N=42,000). Previous work has shown a significant twofold excess of Vietnam service and testicular cancer among human patients seen collectively at three Washington, D.C. area hospitals. Current work shows a significant association of testicular seminoma and ever service in I Corps, the Combat Tactical Zone where the highest elevations of risk have been identified within Vietnam among various human studies. Further, benign prostatic hyperplasia likewise is significantly elevated among Vietnam service MWDs, particularly among those who served in I Corps; canine prostatic carcinoma also is significantly associated with Vietnam service.